Conventionally, a packet routing apparatus such as a layer 2 switch has been utilized as an apparatus which retrieves a transfer path of a received packet. In order to cope with the increased speed in packet communication, it has been effective for the packet routing apparatus to install thereon a memory with which an optimum path may be retrieved in a short time among multiple path candidates. Such a memory may include, for example, TCAM (Ternary Content Addressable Memory) having three values of 0 (zero), 1 (one) and a mask value. The TCAM specifies the path information suitable for the received packets among the multiple path information stored in, for example, a large capacity MAC (Media Access Control) address table based on the header information of the received packets. The packet routing apparatus may use the TCAM to instantly transfer the packets received from different apparatuses to a desired transfer destination apparatus via a retrieved path.
A related technique is disclosed in, for example, Japanese Laid-Open Patent Publication No. 2009-17439.